New Vaccine May Help Combat Several Tick-Borne Illnesses
Lyme disease has recently become one of the
most common infectious diseases in America. According to estimates, more
than 40,000 cases of Lyme disease are reported annually, but experts
say that the actual number of infections could be 10 times greater. The
bacterial infection, which jumps from ticks to humans, could spread
faster in the coming years because of climate change - public health
officials fear.
Caused primarily by the bacterium Borrelia
burgdorferi, the most recognizable sign of the disease is a bull's
eye-shaped rash that develops around the bite after a few days. Other
symptoms include fever, headache, joint pain, and fatigue. If not
treated soon enough, the infection can spread to the joints, heart, and
nervous system and cause severe complications. While Lyme disease can be
treated with antibiotics, there’s no vaccine to give you extra
protection against the most common vector-borne disease in America.
Thankfully, there appears to be some good
news on that end. Yale University researchers have recently developed a
novel vaccine that has shown promise in preventing the spread of Lyme
disease. What’s more, the vaccine may also combat other tick-borne
diseases.
How does the vaccine work?
The researchers explain that the saliva of the black-legged tick Ixodes
scapularis, which transmits the Lyme disease pathogen Borrelia
burgdorferi, contains several proteins. The team focused their research
on 19 different varieties. While searching for the basis of the vaccine,
Yale researchers and a team from the University of Pennsylvania have
analyzed pieces of mRNA that produce all 19 of the saliva proteins.
Incidentally, this is a similar approach to that used by the scientists
who created the COVID-19 vaccine.
In a series of experiments, they tested the vaccine on guinea pigs
bitten by a Lyme disease-carrying tick. All human vaccines directly
target pathogens. However, instead of triggering an immune response
against a particular pathogen, the new vaccine attacks the tick’s
saliva. The study’s authors say that this prompts an immediate skin
response to the bite and therefore limits the amount of time the tick
has to feed and infect the host.
Lyme disease is not the only illness these
insects can carry. There are multiple other tick-borne diseases, and the
researchers believe that this approach provides broader protection than
a vaccine that targets a specific pathogen. They also feel that this
approach can be used together with other traditional, pathogen-based
vaccines to increase their effectiveness.
For the trial, the team attached Lyme-ridden ticks on two sets of guinea
pigs: one that received the vaccine and the unvaccinated control group.
The ticks were removed after the animals began developing inflammation
or a rash. They discovered that, unlike the non-immunized group, the
vaccinated animals developed an immune reaction - redness at the tick
bite area. As long as they removed the ticks right after the redness
started, none of the immunized pigs developed Lyme disease. On the other
hand, almost half of the control group was found to be infected with B.
burgdorferi after the ticks were taken out.
Interestingly, when the investigators
placed a single tick to immunized guinea pigs and didn’t remove it, not a
single animal was infected. Conversely, 60% of the unvaccinated animals
did become infected. Furthermore, the vaccine also prevented the ticks
from feeding aggressively on the immunized animals and caused them to
dislodge from their skin quicker.
The vaccine does have its limits, however. The researchers found that
protection against Lyme disease waned even in immunized animals when
three ticks remained attached to the guinea pigs.
In their report published in the journal Science Translational Medicine,
the scientists note that this vaccine enhances the ability to recognize
a tick bite and partially turns a tick bite into a mosquito bite. “When
you feel a mosquito bite, you swat it. With the vaccine, there is
redness and likely an itch so you can recognize that you have been
bitten and can pull the tick off quickly before it has the ability to
transmit B. burgdorferi,” they add.
Will the new vaccine work on humans?
Now, the most important question is – will
this novel vaccine provide protection against Lyme disease to humans?
The team accepts that this is still an unfinished product, and they need
to conduct a few more comprehensive tests before the vaccine can be
deemed fit for human trials.
In similar experiments using mice, they discovered that the vaccine was
unable to protect against tick-borne infections. According to the study
authors, ticks may have found new ways to feed off of mice. Another
possibility may be that guinea pig skin, like human skin, has more
layers than the skin of mice.
Thus, for now, the vaccine will be going
through further animal trials and possible modifications. If the results
continue to show promise, human trials can then be started. The signs
are positive, and if the vaccine proves to be successful, it will come
as a huge relief for countries that regularly suffer from Lyme disease
and other tick-borne diseases.